ASSAY DEVICES AND THE MANUFACTURE THEREOF

Abstract: An assay sample testing device comprises a porous liquid-permeable carrier strip within a casing, the carrier including a detection zone in which an assay result is revealed by specific binding of a detectable material directly or indirectly to a binding agent immobilised in the detection zone, the casing including internal registration means which cooperatively engages with corresponding registration means associated with the carrier, for example a pin and hole, such that said detection zone within the casing is precisely located in relation to the interlocking means on the casing. During manufacture, the corresponding registration means is used to control accurate formation of the detection zone on the carrier, and accurate placement of the carrier within the casing.

Description: ASSAY DEVICES AM) THE MAMTFACTURE THEREOF This invention relates to assay devices and to improved ways of manufacturing such devices . Many assay devices are now available which comprise a porous carrier material, such as a strip, through which applied sample liquid such as urine can permeate and wherein the assay result occurs by means of specific binding of a detectable material in a precisely-defined region (detection zone) of the carrier, such as a narrow line or small dot, containing an immobilized specific binding reagent. Home-use versions of such devices for the analysis of urine, for example in pregnancy tests and ovulation prediction tests, are now widely available commercially. Many such devices are based on the principles of immunochromatography, and typically comprise a hollow casing constructed of plastics material containing a porous assay strip carrying pre-dosed reagents. The reagents within the device can include, for example, one or more reagents labelled with a direct label, such as a dye sol, a metallic (e.g. gold) sol, a non-metallic element (e.g. selenium, carbon) sol, or a coloured latex (polystyrene) microparticle, which are visible to the eye when concentrated in a comparatively small test area of the strip. The user merely needs to apply a urine sample to one part of the casing to initiate the assay. The assay result becomes visible by eye within a few minutes without further action by the user. Examples of such devices are described in EP-A-291194 and EP-A-383619, the disclosures of which are incorporated herein by reference. Sample collection can conveniently be achieved by means of a bibulous member which forms part of the device and which can readily take up sample liquid, eg. from a urine stream. Optionally the bibulous member can protrude from the casing of the device to facilitate sample application. A particular objective of the invention is to improve the manufacture of assay devices by facilitating the precise locating of a relatively small detection zone within the device. This will have the advantages that less wastage may occur during manufacture by the production of fewer defective devices in which the detection zone is misplaced. Also, the subsequent reading of an assay result in the detection zone is facilitated, because for example an associated optical reading device may not need to "scan" to identify the exact location of the detection zone prior to determining an assay result. In one embodiment, the present invention provides an assay sample testing device comprising a porous liquid-permeable carrier within a casing, said carrier including a detection zone thereof in which an assay result is revealed by specific binding of a detectable material directly or indirectly to a binding agent immobilised in said detection zone and said device casing includes internal registration means which cooperatively engage with corresponding registration means associated with said carrier such that said detection zone within said device casing is precisely located in relation to said registration means on said device casing. For example, said internal registration means comprises a peg or the like, engagable with a hole or depression in said carrier, said detection zone being situated at a precise predetermined location on said carrier relative to said hole or depression. During manufacture of said assay device, said corresponding registration means may be used to facilitate or control accurate formation, e.g. by means of reagent printing techniques, of said detection zone on said carrier. In addition, or alternatively, accurate placement of said carrier within said device casing can be facilitated or controlled by said registration. The invention particulaarly provides a process for the manufacture of an assay device comprising a porous strip within a casing, the strip including at least one detection zone formed by depositing a reagent onto a sheet of porous material prior to subdivision of the sheet into a plurality of identical strips each bearing a portion of the printed reagent, wherein: a) prior to reagent deposition, the sheet of porous material is provided with a plurality of holes or depressions, at least one hole or depression lying in each region of the sheet which will form an individual strip on subdivision of the sheet; b) during reagent deposition, the sheet is held by means of the holes or depressions in registration with a printing means such that deposition of the reagent on the sheet is inn a predetermined position relative to the holes or indentations; and c) following subdivision of the sheet, the assay device is assembled by locating an individual strip within a casing by means of cooperative engagement between said at least one hole or depression and locating means within said casing. The holes or indentations preferably lie along the longitudinal periphery of the sheet. Reagent deposition can involve printing reagent in one or more lines substantially parallel to an array of said holes or indentations. A benefit of providing an internal registration system which ensures precise location of the detection zone within the test device, is that automated manufacture and quality control of the testing devices can be facilitated. If the testing devices are intended to be disposable after individual use, they may need to be manufactured in large numbers at low cost. Internal registration can facilitate automated manufacture and high throughput . Other zones requiring critical placement, such as a control zone, can also be located more precisely if desired by means of the invention. By way of example only, an assay device in accordance with the invention will now be described with reference to the accompanying drawings, of which: Figure 1 shows a general view of a sheet of carrier material, e.g. nitrocellulose paper, during the course of reagent deposition on the sheet and subdivision of the sheet into assay strips. Figure 2 shows an "exploded" view of an assay device of the invention incorporating an assay strip made as shown in Figure 1. Referring to Figure 1, the sheet 100 of porous carrier material is intended to be divided into a plurality of identical assay strips 101 by cutting along central axis A- A and the lateral axes B-B. Parallel lines (102-107) of assay reagents are placed on sheet 100 prior to sub-division. For the purposes of example only, the reagents involved are a first immobilised antibody in lines 102 and 107, and a second different immobilised antibody in lines 103 and 106. Reagent deposition can be by means of a "pen" 108 or the like operated on a computer-controlled "x-y" plotting mechanism (not shown) and fed with appropriate buffered reagent solution via a metered flexible tube 109. If the material of sheet 100 is nitrocellulose, reagents such as antibodies or antigens can be immobilised by simple direct application onto the nitrocellulose, followed by blocking of the sheet material with albumen or polyvinyl alcohol. Following reagent deposition and blocking, two lines 104 and 105 of mobile labelled reagent, such as antigen (e.g. E3G, LH) labelled for example with a particulate direct label such as coloured latex, can be deposited. This deposition can be for example by means of an other pen (not shown) . Alternatively, the labelled reagent (s) can be held in a separate porous pad or the like, rather than being applied directly to the test strip material. In order to achieve precise location of the reagent- containing lines, each longitudinal periphery 110, 111 of sheet 100 is pierced with a plurality of identical small holes 112 each one being situated within the width of a designated strip 113. Holes 112 are made in sheet 100 prior to the deposition of any reagents. The untreated sheet is located on a frame (not shown) or similar operating surface by means of a bar 114 pressed downwardly onto each lateral periphery of the sheet. Only one of these bars is (partially) shown. Each bar has a plurality of downwardly projecting pegs 115, each of which locates precisely into one of the holes 112. The tracking of the reagent-depositing pen 108 is registered with the position of the bars holding the sheet, and accordingly the reagent deposition is made in a predetermined precise line relative to the perforations in the sheet. Following all necessary reagent depositions and other treatments of the sheet, the sheet is subdivided by cutting means (not shown) into individual identical strips 101. Each individual strip therefore contains one locating hole 112 with two reagent-containing lines or reaction zones (e.g. 102 and 103) located relative to hole 112 in precise predetermined positions extending across the width of each strip. At a location remote from hole 112 is a region (e.g. 104) of the strip bearing the mobile labelled reagent. The exact position of the labelled reagent relative to the hole is not critical . Referring to Figure 2, an assay device of the invention comprises a plastics casing having upper and lower halves 200 and 201 adapted to contain the assay strip 101 and also an optional bibulous sample receiving member 202 which can extend out of one end 203 of the assembled casing. In the assembled device as shown the bibulous receiving member 202 overlaps the end 204 of the assay strip adjacent to the deposited labelled reagent. The upper half 200 of the casing includes an observation window 205 through which both detection zones 102 and 103 can be observed from outside the casing. On the inside of the upper half of the casing is a downwardly extending pin or peg 206. The diameter of the downwardly extending pin or peg 206 matches that of the hole 112 in the assay strip 101, so that the strip can be positively located within the assembled device on the peg. Lower half 201 of the casing also includes a result observation window 207 which, in the assembled device lies, directly opposite to the result window 205 in the upper half of the casing. Lower half of the casing also contains means, such as a depression 208, which can accommodate the bottom end of the pin or peg 206 when the two halves of the casing are placed together to make an enclosure. In the assembled device, the act of enclosing the strip and bibulous member between the upper and lower halves of the casing causes the overlapping portions 204 and 209 of the strip and bibulous member to be crimped together to provide a good moisture-conductive junction.

Claims: CLAIMS 1. An assay sample testing device comprising a porous liquid-permeable carrier within a casing, said carrier including a comparatively small detection zone in which an assay result is revealed by specific binding of a detectable material directly or indirectly to a binding agent immobilised in said detection zone, and said device casing includes internal registration means which cooperatively engage with corresponding registration means associated with said carrier such that said detection zone within said device casing is precisely located in relation to said registration means on said device casing. 2. A device according to claim 1, wherein said internal registration means comprises a peg or the like, engagable with a hole or depression in said carrier, said detection zone being situated at a precise predetermined location on said carrier relative to said hole or depression. 3. Process for the manufacture of an assay device according to claim 1 or claim 2, during which said corresponding registration means is used to control accurate formation of said detection zone on said carrier, and accurate placement of said carrier within said device casing. 4. A process for the manufacture of an assay device comprising a porous strip within a casing, the strip including at least one detection zone formed by depositing a reagent onto a sheet of porous material prior to subdivision of the sheet into a plurality of identical strips each bearing a portion of the printed reagent, wherein: a) prior to reagent deposition, the sheet of porous material is provided with a plurality of holes or depressions, at least one hole or depression lying in each region of the sheet which will form an individual strip on subdivision of the sheet; b) during reagent deposition, the sheet is held by means of the holes or depressions in registration with a printing means such that deposition of the reagent on the sheet is inn a predetermined position relative to the holes or indentations; and c) following subdivision of the sheet, the assay device is assembled by locating an individual strip within a casing by means of cooperative engagement between said at least one hole or depression and locating means within said casing. 5. A process according to claim 4, wherein said holes or indentations lie along the longitudinal periphery of the sheet . 6. A process according to claim 4 or claim 5, wherein reagent deposition involves printing reagent in one or more lines substantially parallel to an array of said holes or indentations . 7. A process according to any one of claims 4 to 6, wherein said casing is provided with an observation window through which said detection zone can be observed from outside the casing, location of the strip within the casing ensuring that said detection zone is in a predetermined position relative to said observation window. 8. A process according to any one of claims 4 to 7, wherein the strip carries more than one detection zone. 9. A process according to any one of claims 4 to 8, wherein said locating means within said casing is a peg.

Inventors: MUNDILL PAUL HENRY CHARLES, PRIOR MICHAEL EVANS, MUNDILL, PAUL, HENRY, CHARLES, PRIOR, MICHAEL, EVANS
Applicants: MUNDILL PAUL HENRY CHARLES, PRIOR MICHAEL EVANS, UNIPATH LTD, MUNDILL, PAUL, HENRY, CHARLES, PRIOR, MICHAEL, EVANS, UNIPATH LIMITED
Application year: 1994
Main classification: G01N33
IPC codes: G01N31, G01N33, G01N37